The trackball device, wherein a ball is rotated with a finger and the direction of rotation of the ball serves as the input operation direction and the direction of rotation, is known as an input device for movement operations for cursors or characters that are displayed on a display of a computer or a game machine, or the like; however, the ball requires an installation space commensurate with the diameter of the ball, becoming a hindrance to miniaturization of computers and game machines.
Given this, Japanese Unexamined Patent Application Publication 2004-94450 (Patent Reference 1) and Japanese Unexamined Patent Application Publication 2003-91360 (Patent Reference 2) each disclose an instruction inputting device having detection electrodes for detecting floating capacitance that are disposed on the surface of a spherical insulator, and the input operation on a hemispheric input operation surface of the spherical insulator is detected according to a change in the floating capacitance of the detection electrodes.
FIG. 8 is an oblique assembly diagram of a conventional instruction inputting device 100 as described in Patent Reference 2, wherein a plurality of electrodes 101a are each disposed in parallel on the top surface side of a top substrate 101 made from a dielectric material, and a plurality of electrodes 102a are each disposed in parallel in the direction that is perpendicular to the electrodes 101a, on the top surface side of a bottom substrate 102. At the center of both of the top substrate 101 and the bottom substrate 102, protruding curved surface portions, curved upwards in the figure, are formed for each of the substrates 101, 102, together forming an input operation surface with a protruding curved surface wherein the two are stacked.
Each of the electrodes 101a and 102a is electrically connected to a control circuit 103, where the change in electrostatic capacitance between intersecting ones of the electrodes 101a and 102a at a point of the input operation, caused by an input operation wherein a finger is brought into proximity with the input operation surface, is detected by the control circuit 103, to output the input operation position. For example, a predetermined pulse voltage is applied by the control circuit 103 to the plurality of electrodes 101a and scanned sequentially, and the voltages of the plurality of electrodes 102a that intersect with the electrode 101a to which the pulse voltage is applied are detected. If a finger or another object to be detected is in proximity, then there will be a change in the static capacitance between the specific electrodes 101a and 102a that intersect at the position that is in proximity with the object to be detected, and the position of the operation of the object to be detected on the hemispherical input operation surface is detected from the positions of the electrode 102a wherein there was the change in voltage due to a change in the static capacitance, and the position of the electrode 101a to which the pulse voltage was applied at that time.
In this way, with the conventional instruction inputting device 100 having pluralities of electrodes 101a and 102a laid out in the form of a matrix, there is a problem in that the circuit structure is complex and large because a change in voltage of a large number of electrodes 102a that intersect with each of the electrodes 101a to which a detection voltage has been applied must each be sequentially tested in order to detect the position of the input operation on the input operation surface
Furthermore, because the position of the input operation is detected by reading the change in voltage for all of the positions of intersections of the large number of electrodes 101a and 101b, the detection of the position of the input operation is time-consuming, and when detecting the direction of operation and the direction of rotation of operation of an input operation from the relative change in the position of the input operation, the detection time period is long, so the spacing between the operation positions that are detected will be large, making it impossible to detect these directions of operation with high accuracy.
In particular, when detecting a rotational operation wherein the position of the input operation is rotated along a hemispherical input operation surface, the position of the input operation that is detected as a planar coordinate is detected periodically, and the direction of rotation of operation and speed of rotational operation are calculated from the relative positions and direction of the positions of the input operations that have been detected. The calculations are complex, and the detections are time-consuming.